This invention relates generally to cutting tool assemblies for metal cutting machining having a replaceable cutting head, and more particularly to cutting tool assemblies having an elongated shank for rotary cutting operations.
Cutting tool assemblies having an elongated shank for rotary cutting operations have long been known. It has been proposed in EP 0 298 937 B1, to provide a cutting tool comprising a cutting body and a shaft that supports the cutting body. The cutting body is detachably connected to a locking screw via hook-shaped means. The hooked-shaped means transfers axial forces between the cutting body and the locking screw. Both the cutting body and the locking screw are provided with hook shaped means. Both of the hooked shaped means are provided with recesses and tongues. The recesses and tongues cooperate to permanently transfer rotational movement between the locking means and the cutting body. The locking screw is provided with an externally threaded portion that is connected to an internally threaded recess provided in the shaft. The threads are designed as right hand threads for right hand cutting tools and as left hand threads for left hand cutting tools. The locking screw is movable in the axial direction by relative rotation of the externally threaded portion with respect to the internally threaded recess. The shaft is provided with a conical seat and the cutting body is provided with a circumferential conical portion that is received in the conical seat of the shaft. The cutting body can be inserted in or removed from the conical seat by displacing the locking screw from its innermost position to an intermediate position.
The prior art cutting tool described above suffers from two basic disadvantages. First, to insert or remove the cutting body from the shaft the locking screw has to be displaced from its innermost position to an intermediate position. Second, the cutting body cannot be used in any other type of tool since it is formed with hook-shaped member and therefore it requires the presence of a locking screw having a mating hook-shaped member for coupling it to the shaft.
It is an object of the present invention to provide a cutting tool assembly that substantially overcomes the above-mentioned disadvantages.
In accordance with the present invention there is provided a cutting tool assembly comprising:
a tool shank having a forward end, a rear end and a longitudinal axis A passing through the forward and rear ends, an elongated hole extending axially from the forward end of the tool shank, adjacent the forward end of the tool shank the elongated hole having a conical portion, the tool shank having a first coupling member adjacent the rear end thereof;
an elongated support bar having a forward end and a rear end, with a threaded bore extending axially rearwardly from the forward end thereof, the elongated support bar having a conical portion rearward of the forward end thereof, the elongated support bar having a second coupling member adjacent the rear end thereof, the elongated support bar being removably retained in the elongated hole of the tool shank with the first coupling member coupled to the second coupling member and with at least a section of the conical portion of the elongated support bar being in abutment with the conical portion of the elongated hole; and
a cutting head having a forward cutting portion and a rear threaded portion; the rear threaded portion of the cutting head being threadingly engaged with the threaded bore in the forward end of the elongated support bar.
In accordance with a first embodiment of the present invention, the elongated hole has a threaded portion adjacent the rear end thereof and wherein the elongated support bar has an externally threaded portion adjacent the rear end thereof and wherein the elongated support bar is removably retained in the elongated hole of the tool shank with the externally threaded portion of the elongated support bar threadingly engaged with the threaded portion of the elongated hole, the threaded portion of the elongated hole forming the first coupling member and the externally threaded portion of the elongated support bar forming the second coupling member.
In accordance with a second embodiment of the present invention, the tool shank has a threaded through bore passing through a section of the tool shank, the threaded through bore extending from a side opening in the tool shank to the elongated hole, the elongated support bar being removably retained in the elongated hole of the tool shank by a securing screw threadingly retained in the threaded through bore, the securing screw engaging a locking recess formed in the elongated support bar, the securing screw forming the first coupling member and the locking recess of the elongated support bar forming the second coupling member.
In accordance with a third embodiment of the present invention, the cutting tool assembly further comprises a coupling bar generally cylindrically shaped at least a portion of which has an externally threaded surface and having an axially extending through bore with an internally threaded portion, wherein the elongated hole has a threaded portion adjacent the rear end of the tool shank and wherein the elongated support bar has an externally threaded portion adjacent the rear end thereof and wherein the coupling bar is removably retained in the elongated hole of the tool shank adjacent the rear end thereof with the externally threaded surface of the coupling bar threadingly engaged with the threaded portion of the elongated hole and the elongated support bar is removably retained in the elongated hole with the externally threaded portion of the elongated support bar threadingly engaged with the internally threaded portion of the coupling bar, the internally threaded portion of the coupling bar forming the first coupling member and the externally threaded portion of the elongated support bar forming the second coupling member.
In accordance with a fourth embodiment of the present invention, the cutting tool assembly further comprises a cylindrical sleeve having a non-threaded external cylindrical surface and an axially extending threaded through bore and wherein the elongated hole in the tool shank has a cylindrically shaped rear portion in which the cylindrical sleeve is mounted and wherein the elongated support bar is removably retained in the elongated hole with the externally threaded portion of the elongated support bar in threaded engagement with the threaded through bore in the cylindrical sleeve, the threaded through bore in the cylindrical sleeve forming the first coupling member and the externally threaded portion of the elongated support bar forming the second coupling member.
In accordance with a fifth embodiment of the present invention, the cutting tool assembly further comprises a cylindrical sleeve having a non-threaded external cylindrical surface and an axially extending threaded through bore and wherein the elongated hole in the tool shank has a cylindrically shaped rear portion in which the cylindrical sleeve is mounted and wherein the cutting tool assembly further comprises a coupling bar generally cylindrically shaped, at least a portion having an externally threaded surface and having an axially extending through bore with an internally threaded portion, and the coupling bar is removably retained in the cylindrical sleeve with the externally threaded surface of the coupling bar in threaded engagement with the threaded through bore of the cylindrical sleeve and the elongated support bar is removably retained in the elongated hole of the tool shank with the externally threaded portion of the support bar in threaded engagement with the internally threaded portion of the coupling bar, the internally threaded portion of the coupling bar forming the first coupling member and the externally threaded portion of the elongated support bar forming the second coupling member.
If desired, the elongated support bar is provided with a coolant channel for conducting a coolant fluid, the coolant channel extending axially from the rear end to the forward end of the elongated support bar, and the cutting head is provided with a coolant channel extending through the rear threaded portion thereof and exiting the cutting head at exit openings formed in the forward cutting portion thereof.
If desired, the tool shank of the fourth or fifth embodiments of the present invention is made of cemented carbide.
Typically, the cylindrical sleeve is mounted in the tool shank by heat shrink-fit techniques.
Further typically, the cylindrical sleeve is mounted in the tool shank by soldering.